1. Field of the Invention
The present invention relates to a zoom type lens barrel mounted on an image pickup apparatus such as a digital camera, and an image pickup apparatus having the lens barrel.
2. Description of the Related Art
Conventionally, in a zoom-type lens barrel mounted on an image pickup apparatus such as a digital camera, a plurality of lens units holding lenses are moved in the direction of an optical axis by rotation of a cam cylinder, while the movement of the lens units in the rotational direction is inhibited by a translating cylinder.
In recent years, with the demand for an increase in shooting magnification, the number of lens units have increased, and the length over which lens units are extended have increased, and thus the size of a lens barrel tends to increase. On the other hand, there has been the demand for slimming down of digital cameras, and accordingly, the dimension of a lens barrel in the direction of an optical axis when the lens barrel is retracted has been required to be reduced to the extent possible.
Accordingly, for example, there has been proposed a lens barrel in which cam grooves are provided on an inner peripheral side and an outer peripheral side of one cam cylinder, and a plurality of lens units following the respective cam grooves are relatively moved in the direction of an optical axis to change shooting magnifications (see Japanese Patent Laid-Open Publication (Kokai) No. 2006-078537). Also, there has been proposed a lens barrel in which a front set of lens units and a rear set of lens units are cam-engaged with and held on respective cam grooves formed on cam members in the third row (see Japanese Patent Laid-Open Publication (Kokai) No. 2006-078537).
Further, there has been proposed a method by which followers are provided before and after a lens unit in the direction of an optical axis, and the followers are moved on the same cam cylinder with movement of a zoom lens to ensure movement strokes of the lens unit (see Japanese Patent Laid-Open Publication (Kokai) No. 2007-114531).
Further, according to both Japanese Patent Laid-Open Publication (Kokai) No. 2006-078537 and Japanese Patent Laid-Open Publication (Kokai) No. 2007-114531, if relative movement intervals of lens units in the direction of an optical axis are increased so as to increase the shooting magnification, the dimension of a translating cylinder, which inhibits the rotation of the lens units, in the direction of the optical axis will be increased. As a result, the dimension of a lens barrel in the direction of the optical axis when the lens barrel is retracted will be increased, which inhibits slimming-down of an image pickup apparatus.